1. Field of the Invention
The present invention relates to a wobble plate compressor, and more particularly, to the improvement of a rotation preventing mechanism to prevent rotation of the wobble plate in this type of compressor.
2. Description of the Prior Art
In wobble plate type compressors, pistons are reciprocated in cylinders by conversion of rotational motion of an inclined plate into nutational motion of a wobble plate. This type of compressor is well known in the art. Inclined wobble plate compressors are the variable-displacement compressors, wherein the angle of an inclined plate relative to a drive shaft is variable and the displacement of the pistons can be controlled by controlling the angle of the inclined plate. These compressors are also well known in the art, and one example is disclosed in unexamined Japanese Patent Publication SHO 56-77578.
In such variable-displacement wobble plate compressors, rotational motion of the wobble plate must be prevented. FIGS. 7 to 9 show a conventional rotation preventing mechanism for a wobble plate. A hole 3 is formed in the lower portion of the wobble plate and extends in the axial direction of wobble plate 1 from its periphery.
Cylindrical block 5 is disposed in hole 3. A pair of arc-shaped caulking pieces 7 are provided around the opening portion of hole 3. Cylindrical block 5 is retained in hole 3 by bending caulking pieces 7 in the direction of the bottom surface of the cylindrical block. Vertical groove 9 is defined in cylindrical block 5 and extends from the bottom surface of the block in the axial direction of wobble plate 1. One side of guide plate 11 is slidably fitted into groove 9. Cylindrical block 5 can rotate in hole 3 in its circumferential direction relative to wobble plate 1. Thus, wobble plate 1 can move nutationally.
In this type of rotation preventing mechanism, hole 3 of wobble plate 1 and caulking pieces 7 constitute a system for retaining cylindrical block 5, and preventing it from being dislodged from hole 3. This prevents the rotation of wobble plate 1.
Another conventional rotation preventing mechanism is shown in FIGS. 10 to 12. Pin 13 is attached to cylindrical block 5 near the head of the cylindrical block. The ends of the pin project from the surface of the cylindrical block in the radial direction. A hole 3 is formed in wobble plate 1, with openings 3a and 3b extending in the depth direction of hole 3 at both sides of the wobble plate. Further grooves 3c extend in the circumferential direction on the inner surface of hole 3 for containing therein the ends of pin 13. When cylindrical block 5 is assembled, pin 13 is matched with openings 3a and 3b. The cylindrical block is then inserted into hole 3. Finally, the ends of pin 13 are engaged with groove 3c by rotating the block. Thus, cylindrical block 5 is retained in hole 3 and may not be dislodged from the hole.
In this type of rotation preventing mechanism, pin 13 and groove 3c constitute a system for retaining cylindrical block 5 in hole 3. Also, rotation of wobble plate 1 is prevented by engaging guide plate 11 with vertical groove 9. The cylindrical block 5 allows nutational motion of wobble plate 1 since pin 13 slides along groove 3c accompanying the nutational motion of the wobble plate (unexamined Japanese Patent Publication SHO 63-205471).
However, there are problems associated with the prior art retaining systems. In the retaining system of the rotation preventing mechanism shown in FIG. 7, cylindrical block 5 is retained in hole 3 by bending caulking pieces 7. Thus, the caulking pieces are deformed if the block is detached from the hole for any reason. If this happens, the wobble plate cannot be reused, and cylindrical block 5 cannot be disassembled. If the cylindrical block 5 is replaced, the wobble plate 1 must be replaced at the same time.
In the retaining system of the rotation preventing mechanism shown in FIG. 10, it is difficult to form groove 3c. Moreover, since pin 13 is brought into contact with wobble plate 1, it is difficult to provide a durable contact area. A large stress is applied to the contact area when cylindrical block 5 slides along guide plate 11. Therefore, pin 13 and/or groove 3c are likely to abrade in a relatively short time.